High idle and fans running at end of journey - no regen

[gergely]

Hi folks, I have experienced high idle and fans running after rides during summer without DPF regen actually happening at that time - sometimes even checked with diagnostic tool to be sure. I assume it may be due to the fact that it's quite hot weather, used A/C, it must be very hot in the engine bay but it's still strange.
Wondering if this is normal or does it mean somewhat limited cooling capacity (although no visible signs of it ever experienced - water temp gauge never moved over the normal (but I know that doesn't mean much), oil temps sometimes close to 120C but that's on higher loads (like highway+hills)).
I drive the van much less in this cold weather but still having enough samples to see this is happening much less - almost never - with ambient temperatures being sub +10-15C. In summer it's often around +30C or even higher.

Can I do something to diagnose this using OBDeleven (which I have) given that I don't really WANT to spend time diagnosing it if it seems normal? Also, is it sane to think about making airflow better around the engine by removing some plastic covers underneath the engine bay and/or cleaning AC radiator (externally) so it has more airflow through it reaching engine cooling radiator? Anything else to consider for hot weather use?

I'm afraid that you folks over in colder climates (especially you, @mmi ) don't experience such behaviour too often but let's see what you guys think about it.

 

[Pauly]

What makes you so sure it’s not doing (or just done) a regen

 

[Dellmassive]

What van spec?

T6, T6.1?.. what engine.

Sounds like typical Regen.
.
The van should do it every 100 miles or so


I use VAG DPF on my phone to check regens.
...

I suppose it's possibly engine heat .... But we don't see 30c much in the UK.
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[Dellmassive]

Some of our members are based in Europe, Spain etc.

May be they can comment on high temps and fans

 

[gergely]

Yeah thanks for the responses which lean me towards still experiencing a regen (or part of it).

@Pauly can't be 100% sure all the time it's not a regen, sometimes it certainly is. Other times I have checked with OBDEleven something like current regen time (or smth like that) parameter in the Engine live data which is displayed in secs and is counting when a regen is actually happening.

@Dellmassive fair point, although it's in my signature I could have mentioned the van being a T6 150PS with sub (but close to) 100k miles on the clock. DPF health according to soot levels seems to be okay. Well, I didn't know regen happens so often and as I see the symptoms of it less often in cold weather made me suspicious about something else. I may be wrong.
Also I would love to have an app like VAG DPF and it seems there is an iOS alternative to it but don't want to get a separate OBD reader as the OBDEleven one is said not to work with it. Anyways, OBDEleven, even if in a more complicated way can still tell me whether it's a regen.

 

[Salty Spuds]

Yeah thanks for the responses which lean me towards still experiencing a regen (or part of it).

@Pauly can't be 100% sure all the time it's not a regen, sometimes it certainly is. Other times I have checked with OBDEleven something like current regen time (or smth like that) parameter in the Engine live data which is displayed in secs and is counting when a regen is actually happening.

@Dellmassive fair point, although it's in my signature I could have mentioned the van being a T6 150PS with sub (but close to) 100k miles on the clock. DPF health according to soot levels seems to be okay. Well, I didn't know regen happens so often and as I see the symptoms of it less often in cold weather made me suspicious about something else. I may be wrong.
Also I would love to have an app like VAG DPF and it seems there is an iOS alternative to it but don't want to get a separate OBD reader as the OBDEleven one is said not to work with it. Anyways, OBDEleven, even if in a more complicated way can still tell me whether it's a regen.

what is your oil temperature when this happens? you should be able to se it on the MFD, if you have one.

 

[gergely]

what is your oil temperature when this happens? you should be able to se it on the MFD, if you have one.

Hmm, oil tends to be quite hot to my taste but reading through the forums more than a few times and it seems normal (Around 110C on highway, close to but below 120C when on hills, pushing it or towing). When this happens oil is usually up to normal operating temps: exiting highway and stopping in a few miles afterwards, cooling down to around 100C while on shorter runs a bit below. TBH I don't have a proper list of oil temps when this happens just the general observation that this happens when engine is already up to operating temps which happens very quickly on those hot summer days.

 

[Salty Spuds]

Hmm, oil tends to be quite hot to my taste but reading through the forums more than a few times and it seems normal (Around 110C on highway, close to but below 120C when on hills, pushing it or towing). When this happens oil is usually up to normal operating temps: exiting highway and stopping in a few miles afterwards, cooling down to around 100C while on shorter runs a bit below. TBH I don't have a proper list of oil temps when this happens just the general observation that this happens when engine is already up to operating temps which happens very quickly on those hot summer days.

Is the temp gauge bang on centre or to the high side? I'm just trying to establish if the engine is running hotter than normal. The highest I've seen my oil temp is 110C and that was towing a 2000kg trailer up a hill in Portugal. My temp gauge is always bang on centre. Personally I think your problem sounds like an incomplete regen. If you take the van for a long run with a 20 minute low gear/high rev finish at the end, do you still get the same fan behaviour?

 

[Dellmassive]

Re signature....

I've seen it now.... But signature is not visible on mobile devices unless landscape or on pc etc.

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...

 

[gergely]

Is the temp gauge bang on centre or to the high side? I'm just trying to establish if the engine is running hotter than normal. The highest I've seen my oil temp is 110C and that was towing a 2000kg trailer up a hill in Portugal. My temp gauge is always bang on centre. Personally I think your problem sounds like an incomplete regen. If you take the van for a long run with a 20 minute low gear/high rev finish at the end, do you still get the same fan behaviour?

It's bang on centre.

Well, considering that in summer I'm using the van more, including shorter journeys - as my main objective is to avoid cold operation as much as possible and that's given in 5km when it's 30+C outside... - it may be incomplete regens. Engine heats up to temp and the trip finishes soon after.

Can't tell how it behaves with the proposed scenario as DSG is crazy about keeping low revs unless put into S or M which I tend not to do. TVS DSG remap due soon and I can exercise more caution on the revs at the end of a journey too. Will see.

Re 110C max oil temp, I would be happy with it. Oil service was just done and those higher temps I experienced during summer were with previous oil which I have not much info about as service was done at the previous owner yet. No excessive oil consumption though potentially be caused by too thin oil doing subpar job on lubricating engine parts as well as clogging up DPF causing more frequent regens. Again, will see on the second summer coming with the van better knowing its parameters.

 

[gergely]

Re signature....

I've seen it now.... But signature is not visible on mobile devices unless landscape or on pc etc.

Good info, thanks!

 

[Salty Spuds]

It's bang on centre.

Well, considering that in summer I'm using the van more, including shorter journeys - as my main objective is to avoid cold operation as much as possible and that's given in 5km when it's 30+C outside... - it may be incomplete regens. Engine heats up to temp and the trip finishes soon after.

Can't tell how it behaves with the proposed scenario as DSG is crazy about keeping low revs unless put into S or M which I tend not to do. TVS DSG remap due soon and I can exercise more caution on the revs at the end of a journey too. Will see.

Re 110C max oil temp, I would be happy with it. Oil service was just done and those higher temps I experienced during summer were with previous oil which I have not much info about as service was done at the previous owner yet. No excessive oil consumption though potentially be caused by too thin oil doing subpar job on lubricating engine parts as well as clogging up DPF causing more frequent regens. Again, will see on the second summer coming with the van better knowing its parameters.

We have DSG on the van & on our family car. They both regularly get put into manual & knocked down a couple of gears on the motorway, & get an “Italian tune up”

 

[mmi]

I'm afraid that you folks over in colder climates (especially you, @mmi ) don't experience such behaviour too often

Oh yes, we do have hot weather regularly - not every year though

I have experienced high idle and fans running after rides during summer without DPF regen actually happening at that time - sometimes even checked with diagnostic tool to be sure. I assume it may be due to the fact that it's quite hot weather, used A/C,

I believe the snippet below explains your observations - a capture from A/C controller - showing that A/C controller has requested both high idle and also activation of engine's coolant fan.


Note: A/C controller reports engine RPM at resolution of 100 RPM thus here shown "only" 900 instead of the actual elevated 970 RPM.
There are also other factors which can call for elevated RPM, e.g. high alternator load - discharged battery, windscreen heater, etc.

Wondering if this is normal or does it mean somewhat limited cooling capacity (although no visible signs of it ever experienced - water temp gauge never moved over the normal (but I know that doesn't mean much),

It's perfectly normal. For the A/C to produce cold into cabin it must dissipate the "collected" heat from cabin via condenser (the element that looks like a radiator - in front of engine's radiator). To take the heat away from the condenser running the coolant fan is necessary - especially at standstill.
Better explained e.g. here

Air Conditioner Diagram Car

Air system conditioning components evaporator compressor refrigerant valve condenser expansion cars old four main cooled basics transfers elsewhere using Car air conditioning system : principle and working How does a car air conditioner work? Car air conditioner refill diy

worksheetaka11288qr.z21.web.core.windows.net

cleaning AC radiator (externally)

That's always useful - especially if it's covered with dirt, insects, etc. And, of course having the A/C serviced (refrigerant refill) every now and then - every 2-3 years perhaps.

I drive the van much less in this cold weather but still having enough samples to see this is happening much less - almost never - with ambient temperatures being sub +10-15C.

The A/C doesn't normally do much at those temperatures...

 

[gergely]

I believe the snippet below explains your observations - a capture from A/C controller - showing that A/C controller has requested both high idle and also activation of engine's coolant fan.

View attachment 274158
Note: A/C controller reports engine RPM at resolution of 100 RPM thus here shown "only" 900 instead of the actual elevated 970 RPM.
There are also other factors which can call for elevated RPM, e.g. high alternator load - discharged battery, windscreen heater, etc.

Oh yes, thanks so much! Actual data instead of guesswork, as always. Much appreciated.

Unfinished regens - which are not a factor of ambient temperature but the fact that I use the van more often even for short rides during summer - should also be taken into account so all other responses were useful too. But knowing that A/C itself can request high idle is very useful!

Fans running when it’s hot was not a surprise but I didn’t even think about a relationship between high idle and A/C. I see the data but don’t really get why high idle is requested by the A/C. Suspect that it’s down to the fans needing high current therefore alternator must work hard and high idle supports this? Perhaps…

 

[mmi]

why high idle is requested by the A/C.

It's the power/torque needed to run the A/C compressor. To generate the required cooling power at low engine revs would put quite a stress on the auxiliary belt - making it slip/squeak.

 

[gergely]

It's the power/torque needed to run the A/C compressor. To generate the required cooling power at low engine revs would put quite a stress on the auxiliary belt - making it slip/squeak.

Okay so test case is to simply turn off A/C at the end of a ride and see. Just have to wait a few months to get up to proper temperature.

Thanks @mmi as always!

 

[n10n]

And, of course having the A/C serviced (refrigerant refill) every now and then - every 2-3 years perhaps.

OT but I just had this done first time in January for my 2018 van with regular service at the dealer. Only couple of grams lost so was kind of waste of money. I always have A/C on througout the year.

 

[Howzat]

It's the power/torque needed to run the A/C compressor. To generate the required cooling power at low engine revs would put quite a stress on the auxiliary belt - making it slip/squeak.

I've experienced this too in hot weather with the AC on.

 

[mmi]

I always have A/C on througout the year.

Me too- almost...

 

[n10n]

Me too- almost...

View attachment 274176

Yes I should have said I have A/C switched on throughout the year.

"Antepenultimate" - now there's a word monster if I've ever seen one!

Have you noted at which ambient temperature A/C is cut off? Also any guesses why it does that? I think the freezing point of R1234yf is well below -100°C, can't be due to that. Too much condensation and it would be forming ice bergs?

This in Finnish but had to check - 157€ for the pleasure, 810g emptied, 830g filled.